The unique value proposition of the PreSonus AudioBox 44VSL ($300 retail) recording system is that it uses your computer’s CPU to perform the real time compression, reverb and other effects normally only possible with much more expensive mixers that deploy DSPs to perform these effects in real time.
In fact, VSL stands for Virtual StudioLive, referring to PreSonus’ own DSP-driven mixers that produce real time effects but start at $1,300. In addition to the recording hardware, the 44VSL comes with two software programs; the VSL program that mimics the mixer controls for the channels available in the unit, and supplies the DSP-like functionality of the StudioLive mixer, plus Studio One Artist, a multi-track recording and editing program. The two programs operate independently of each other; you control the hardware with the VSL program, and record with Studio One. I spent most of my time with the VSL program.
The 44VSL hardware is a book-sized unit with inputs and controls on the front and outputs-including the headphone jack-on the back. It’s an AC-powered product that connects to your computer via USB, but doesn’t draw power from the connection. The four inputs are XLR-1/4” combo jacks in two pairs; inputs one and two have high-impedance 1/4" connectors for instruments plus XLR connectors for microphones, and inputs three and four are microphone/line inputs. All four XLR mics inputs can push 48V phantom power, but the single switch is enabled/disabled globally. Outputs include left and right Main outputs, four line outputs and a headphone jack. There is also MIDI in and out which I didn’t play with.
Each input has a separate volume control with peaking indicator, and there are separate knobs for controlling output volume to the Main and headphone outputs. You can control volume for the 3-4 outputs via a separate fader only in the VSL software, with outputs 1-2 controlled by the Main fader on either the hardware itself or the VSL software.
The only other hardware control is an Input/VSL knob that lets you mix the original input audio with the processed audio from VSL. When you drive the unit with the VSL software, the program tells you to park the knob at full VSL, which is where it stayed for the bulk of my testing. When used without VSL, you can turn the knob over to input for zero-latency monitoring, without the DSP effects, of course.
I spend most of my time around the VSL interface shown in Figure 1. As you can see, there are eight input racks; four from the VSL44 hardware inputs, and four from your DAW, which stands for digital audio workstation and essentially means a multitrack audio editor like Studio One. Accepting input from the DAW means that you can build a song track by track, monitoring what you’ve previously laid down while recording additional tracks.
Each track has a fader, mute, and solo controls, a stereo panner, plus a polarity reverse switch on top and a high pass filter. Press the Post button atop each track and you apply the effects applied by the VSL to the audio captured by the DAW. Leave it unchecked and the audio is captured without any effect, leaving pristine source for subsequent sweetening.
The first two grey tracks to the right of the inputs are FX send buses; there you can collect sets of effects to apply to the different tracks using the A/B controls just above the stereo mix control. The controls just above these marked 3/4 control the levels from that track that are sent to auxiliary outputs 3 and 4. Using these controls, you can send a different mix to a performer connected to these outputs than what’s heard by the performer listening via the headphone jack. In many studio or especially live scenarios, this is a very key requirement for hardware like the 44VSL fulfills, since the guitar player may wish to hear a different mix than the lead vocalist. Continuing in the VSL interface to the right, the next track controls Outputs 3/4, the last track the Main output.
All this is reasonably standard. The special sauce involves the three boxes above each track. Here you can apply the so-called Fat Channel effects, including a gate, compressor, limiter, and three band equalizer for every input-whether from the hardware or DAW- and every output, plus the two FX buses. These are the effects that will be applied in real time, primarily for monitoring purposes, though as mentioned, they can also be recorded with the audio.
As you can see on the right in Figure 1 (above), PreSonus supplies multiple Fat Channel presets for different instruments and vocalist types, which you can customize at will and then save for reuse. You can also capture several Fat Channel presets into a scene file for subsequent reuse, which is helpful when creating inputs for multiple instruments or vocalists.
Of course, the key to Fat Channel operation is latency, or the delay caused by having to transfer the audio stream to and from the computer to apply the DSP-like effects, plus all the associated analog to digital and digital to analog conversions. Specifically, if there’s too much delay between the original audio input and the processed audio output it’s tough to use the output for monitoring. You control latency via a performance slider in the VSL Setup window. I tested on an eight-core Mac Pro and found the USB Driver setup locked into the Fastest performance setting, which is where I left it for my tests.
Obviously, the speed of your computer may impact latency; I tested on the Mac Pro because that’s the computer I use for many voiceovers that I produce for Camtasia tutorials, and also where I perform basic mixing for radio advertisements and some musicians. In my most challenging test, where I recorded two tracks (one guitar, one vocal) while playing back four tracks from Studio One, all with Fat Channel effects applied, latency was imperceptible and CPU utilization averaged under 15%. So while I wouldn’t try this on a single core notebook, the 44VSL should perform well on most dual-core and certainly quad-core and faster computers.
In my voice-over work, where I always apply some compression and perhaps a bit of reverb, I found it very helpful to be able to monitor this in real time, though I did record without the effects applied so I could process off-line in my DAW. For the record, I performed most of this testing within Adobe Audition, my DAW of choice, which worked perfectly with the AudioBox 44VSL. The analog to digital conversion in all tests was excellent; clear, sharp and noise free, and better than I’ve been able to produce with Firewire-based recording gear from a different vendor who will remain unnamed.
Overall, I was impressed with the 44VSL; while it’s more than I need for my voice-related work, the AudioBox 22VSL, which costs $199 with a similar feature set but only two inputs, would be ideal. At the other end of the spectrum, PreSonus offers the 1818VSL, with 18 inputs for around $500. Whatever the size of your needs, if you’re looking for an inexpensive product that can produce real-time effects for monitoring, or push out multiple different mixes for your performers to monitor, check out the PreSonus VSL line.
Jan Ozer is the author of 13 books on the streaming media industry. Interested in reviewing a product for your peers? Email us at AVTIntern@nbmedia.com.